Improving Wet Bonding Performance of Orthodontic Brackets with Tannic Acid

Abstract

<p>Objective: This study aims to explore the application of tannic acid (TA) in orthodontic bracket bonding materials to enhance the bonding performance in moist oral environments.<br></p><p>Methods: The study was designed as an in vitro experiment. Two hundred premolars were collected and divided into four groups to compare the wet bonding performance of a commercial moisture insensitive primer (MIP, 3M Unitek, American) alone and with added TA (Macklin, China) at concentrations of 0.04 mg/µl, 0.08 mg/µl, and 0.12 mg/µl. To simulate moisture oral conditions, 5µl of artificial saliva was applied before employing a standardized procedure to bond brackets to the center of each premolar’s buccal surface. The bonding performance were evaluated through shear bond strength (SBS) and adhesive remnant index (ARI), both immediately and after 2000 thermal cycles of aging. Scanning electron microscopy (SEM) was utilized to analyze the microscopic structure of the bonding interface and to assess the presence of any enamel defects. Statistical analyses were performed using ANOVA and post-hoc tests to determine the significance of the results.<br></p><p>Results: Adding TA into MIP did not significantly alter the adhesive’s cytotoxicity and degree of conversion. TA significantly enhanced the SBS of brackets in moist environments, with the 0.08 mg/µl concentration showing the most pronounced effect. Additionally, the ARI value in the TA group was higher compared to the control group. Consistent results were observed for both immediate bonding and thermal cycling. SEM analysis revealed that the adhesive mixed with TA formed better integration with the resin, and none of the four groups observed any enamel defects.<br></p><p>Conclusion: Incorporating TA, particularly at a concentration of 0.08 mg/µl, into MIP significantly improves orthodontic bracket bonding performance in the moist environment.</p>